Person of Interest took a shocking turn when the beloved character, Carter, was killed. After struggling to deal with her death, Finch and his team have just begun to move on.

At the CBS Television Critics Association Winter Tour, I sat down and spoke with Executive Producers Jonathan Nolan and Greg Plageman about replacing the heart that Carter brought to the show, the characters upcoming journeys and the possibility of more machines out there.

Since Carter's death the show's turned dark without her in the mix. Going forward is there going to be a way to bring some of the heart that she had back to the show?

Nolan: Carter definitely brought a warmth. Root is plenty warm [laughs]. The show has a darkness for the last spell naturally because we lost the character, fall out from that, and wanting to play that true to the audience. We didn't want to have this momentous thing happen and then next week say "Yeah, moving on." We've played through that storyline. I think [the last episode] went a long way to addressing that issue. The sparks of warmth between all of our characters have always been there.

The first season that dynamic between Finch and Reese really coming alive for people in small ways throughout. Exchanges about Eggs Benedict being Finch's favorite breakfast and Reese thanking him for giving him a job. These tiny -- compared to other shows absolutely -- subtleties of relationships between say Finch and Reese, Reese and Shaw, Finch and Bear.

The short answer to your question being Bear, Shaw and Hersh. Those small pieces of warmth, those glimmers you see between the characters, that's where the show has always lived from the beginning. Even the first half of the first season, Carter was actually pursuing Reese and Finch. It's always been a way that the show works.

Carter was a huge character for us on the show and we didn't take heading in that direction storywise lightly. But the audience wants -- well, I wouldn't speak for the audience -- the writers, we're the first audience for the show, we aim to keep ourselves excited and the way that happens is through change and challenge. And challenging our characters in this way was something we had long wanted to do. Besides if we killed off Fusco, everyone would have seen that coming.

Plageman: I think to a degree the loss of Carter affected Fusco so dramatically in the Devil's Share. The transformation of Fusco in that storyline the climax of that episode was so powerful, I think it was abundantly clear that Fusco was never going to be quite the same.

I think the moral compass that Carter represented on our show -- that torch went to Fusco. I think our audience has always sort of rooted for Fusco's character to sort of become a better man and to a degree that loss of Carter was the thing that drives him now.

For the second half of the season, how do you see the character arcs as far as interaction between characters? For example, is Shaw is going to grow and interact with the other characters?

Nolan: I think Shaw's interesting because she's not a character capable of traditional emotional growth in the way that's become such a hackney thing around television. In the way which Fusco has grown in an unconventional way on a television show. We've taken Fusco, who was a bad guy in the pilot, and slowly, assiduously turned him into a character who's a fan favorite. And, Carter's death was the conclusion of an arc for Fusco which became redeemed.

Shaw is different. Shaw is like a hot knife through butter. She's just Shaw. Her emotional -- or lack of emotional life -- as articulated in the first episode in which she appeared. She very clearly has a personality disorder which prevents her from being happy, smiley, but even within that Shaw, the writers have found ways elucidate the ways in which that character can connect with people.

For her it's not so much a matter of growth so much as the context change and us seeing the tiny fragile connection she makes with Reese and Finch. Again our show is really about these very private, very damaged people and the tiny, fragile relationships that they have with each other as they try to help other people. We imagine we'll see that growth with her character as we have seen with our other characters.

Root is a fun example of a character who has truly gone through a transformational growth as a character. Again, from a villain to ... I wouldn't really call her an ally at this point, but something more in the space of an uneasy alliance that is formed now between Finch, Root, Root and the rest of our heroes. We love playing with that dynamic of take a bad guy turn him into a good guy. Take a good guy go the other way. And we've got lots more room to explore.

Is Root going to be able re-acclimate herself back into society now that she's had these interactions with the machine?

Nolan: Definitely not. We've got lots of places to go with Root, but re-acclimation is not --

Plageman: No, I think if anything, her run in with Control and essentially being maimed by Control will make Root even more determined than ever that no one will ever be able to sever her tie with the machine. And that she'll do everything in her power to enforce that communion that makes Harold Finch so uncomfortable.

With the introduction of the second machine, does that open the possibility that there could be others down the road?

Nolan: I think in the second half of the season, we want to deal with the question that the machine in unique and amazing, but is it really unique? Certainly the arms race that the Americans enjoyed, the metaphor for AI, we drag that out a lot. The Manhattan Project is an appropriate one for many different reasons. And if we look at that metaphor, the Americans enjoyed a tactical advantage of being the soul nuclear superpower for about five years. And, then the Soviets had the bomb, the English, the French, the Chinese, Pakistan, India. It's propagation. And there's no reason to imagine the same wouldn't be true of AI.

I think where the show is playing in interesting territory is the idea of AI as discrete entities is itself a little challenging, but that's the ones we're looking for. For three years, right, the machine has been unique. What's the possibility of something coming along that's similar and what would that be and how would that play out. So we're playing with that possibility in the second half of the season.